MECHANICAL EFFICIENCY OF THE HUMAN BODY 105 
and his associates were those of turning a brake ergometer or of moving the 
body through a given distance, as in using a treadmill or climbing a mountain. 
The most complete collection of the results obtained in the various experi- 
ments carried out by the Zuntz school in which the forward and upward 
progression of the body was studied has been brought together by Durig.* 
Durig's data include the experiments of Zuntz and Schumburg 6 on the 
treadmill, the extensive series reported by Zuntz, Loewy, Muller, and Cas- 
pari, c the experiments of Frentzel and Reach, d and those of Leo Zuntz.' 
These, as well as Durig's own experiments, were all carried out by the Zuntz 
method. The results obtained by Burgi f under Kronecker's direction and 
by an entirely different method, in which onlyvthe carbon dioxide was deter- 
mined, have also been painstakingly recalculated by Durig." The efficiency, 
which was in all cases obtained by deducting the metabolism incidental to 
forward progression from that during climbing, ranged from as low as 19 per 
cent in one or two experiments with Burgi to as high as 46.5 per cent with 
Kolmer in the treadmill experiments.* 
The experiments made by Durig * and his co-workers showed efficiencies 
on the treadmill as high as 37 per cent. In practically all experiments the 
effect of velocity on the speed was noticeable, but Durig considers that an 
average value for the efficiency is 31 per cent. Of special interest is the notice- 
able influence of training apparent in these experiments. The several groups 
of experiments in which Durig himself was the subject are worthy of special 
note. The average net efficiencies in these ranged from 34.9 per cent shown 
when he was walking on a treadmill in Vienna with an inclination of 21.6 
per cent, to 21.2 per cent when walking along a path on Monte Rosa with an 
inclination of 15.5 per cent. In these computations the work of forward 
progression was deducted, so that the efficiency is based solely upon the equiv- 
alent of lifting the body through a given height. During the experiments 
made at Neuwaldegg in summer, in which the path had an inclination of 
16.4 per cent, Durig showed 31.1 per cent efficiency. Of his three collabora- 
tors, all traveling on the same path, Kolmer showed 30.3 per cent, Rainer 
31.7, and Reichel 30.1 per cent efficiency. 
Several series of experiments in Zuntz's laboratory, in which the brake 
ergometer or the Gartner ergostat was used, were those of Katzenstein/ 
Loewy,* Heinemann,* and Frentzel and Reach. m Later, in reporting an 
interesting series of experiments on the energy n required to rotate a centrif- 
ugal machine (a cream separator), Reach ° summarized the earlier work and 
showed that Katzenstein's results indicated a gross efficiency of from 13 to 19 
per cent, and a net efficiency of 25.4 per cent. Heinemann's results show a 
net efficiency of 20.6 to 25 per cent. Reach found in his experiments that 
a Durig, Physiologische Ergebnisse Monte Rosa-Expedition. Ueber den Gaswechsel beim Gehen, Denkschrift 
d. nxath.-natur. Klasse d. Kaiserl. Akad. d. Wiss., Wien, 1909, 86, p. 294. 
o Zuntz and Schumburg, Pfluger's Arcbiv, 1896, 63, p. 484. 
c Zuntz, Loewy, Mailer and Caspari, Hohenklima u. Bergwanderungen, Berlin, 1906. 
Frentzel and Reach, Pfluger's Archiv, 1901, 83, p. 477. 
« A. Loewy, J. Loewy, and L. Zuntz, Pfluger's Archiv, 1897, 66, p. 497. 
/ Burgi, Archiv f. Phvsiologie, 1900, p. 509. 
9 Durig, loc. cit., p. 301. 
ft Durig, loc. cit., pp. 299 and 301. 
* Durig, loc. cit., pp. 340-347. 
J Katzenstein, Pfluger's Archiv, 1891, 49, p. 330. 
t Loewy, Pfluger's Archiv, 1891, 49, p. 405. 
1 Heinemann, Pfluger's Archiv, 1901, 83, p. 441. 
m Frentzel and Reach, Pfluger's Archiv, 1901, 83, p. 477. 
n Erroneously- reported as "rohe Wirkungsgrad " by Reach. Biochem. Ztschr., 1908, 14, p. 445. 
o Reach, Landw. Jahrb., 1908, 37, p. 1053; also Biochem. Ztachr., 1908, 14, p. 430. 
